FIG. 1 illustrates a CO.sub.2 laser scalpel of an optical fiber type as described in the article entitled "Infrared Optical Fiber for Energy Transmission" contributed by M. Ikedo et al. and printed in "Studies on Laser" No. 11, vol. 11 published on Nov. 30, 1983 by the Japanese Laser Institute. In case of CO.sub.2 laser scalpel of an optical fiber type, since the infrared fiber which normally allows the infrared light such as CO.sub.2 laser light or the like to be transmitted therethrough will not allow the visible light to pass therethrough, the laser light as the collimation light is introduced from the area around the circumference of the infrared fiber. In FIG. 1, numeral 101 designates the infrared fiber as above mentioned; numeral 102 the metallic tube which covers the area except the tip end portion of the infrared fiber 101; numerals 103 and 104 two optical fibers for the collimation light which serve to conduct the collimation light; numerals 105, 106 micro lenses which are respectively mounted at the emission ends of the optical fibers 103, 104 for the collimation light and condenses the collimation light so as to orient the collimation light to the optical axis of the infrared fiber 101; numeral 107 the first condensing lens which is provided in front of the infrared fiber 101 and the micro lenses 105, 106; numeral 108 the second condensing lens which is provided in front of the first condensing lens 107; and numeral 109 a hollow outer tube which supports the infrared fiber 101 at the portion adjacent to the emission end thereof by way of a metallic tube 102, supports the output end of the optical fibers 103 and 104 for the collimation light as well as the micro lenses 105 and 106 and supports both condensing lenses 107 and 108 so that the optical axis of the condensing lenses 107 and 108 may collide with the axis of the infrared fiber 101. Further, the condensing lenses 107 and 108 and other elements are so arranged that the laser light 110 and 111 for collimation emitted from the micro lenses 105 and 106 and the laser light 112 for surgical operation purposes emitted from the infrared fiber 101 are focused at the identical spot 113 formed in front of the second condensing lens 108 by way of the first and second condensing lenses 107 and 108.
In the conventional infrared fiber cable constructed as above mentioned, when the collimation beam lights 110, 111 are emitted through the micro lenses 105, 106, these collimation light beams 110, 111 pass over the location adjacent to the tip end portion of the infrared fiber 101. As the result, there has been such a problem as the infrared fiber 101 which is photosensitive would be markedly deteriorated. On the other hand, it may be also conceived that the collimation light beams 110, 111 are caused to emit from the outside of the emission end casing 109 in order to prevent the infrared fiber 101 from being deteriorated. However, this concept has caused such a problem as to degrade maneuvability of the emission end of the infrared fiber. Further, the laser beam for collimation must pass through the center of the emission end of the laser. Moreover, in case of the CO.sub.2 laser scalpel of optical fiber type, an infrared fiber is usually used. However, the infrared fiber will not allow the visible light to pass therethrough, and consequently it often happens that the collimation light is introduced around the circumference of the infrared fiber. In this sort of construction, there has been such a problem as an apparatus for preventing erroneous emission cannot be incorporated. The detailed description will follow in this respect.
FIG. 2 is a schematic illustration of the erroneous emission preventive apparatus for a laser scalpel provided with an optical path of a conventional multi-articulation mirror manipulator type (refer to the Japanese Patent Public Disclosure Gazette No. 116350/83). In FIG. 2, numeral 200 designates the object to be surgically operated; numeral 201 the emission end for the laser light provided at the tip end of the laser scalpel adapted to apply the laser to the object 200 to be surgically operated by emitting both visible laser light for collimation and the invisible laser light for surgical operation; numerals 202 and 203 light detectors disposed at the position to receive the output light from the respective inner layer and outer layer optical fibers to be described later which are secured to the laser emission end 201 adapted to receive and conduct the collimation laser light reflected by the object 200 to be surgically operated; numerals 204 and 205 preamplifiers the inputs of which are connected respectively to the outputs of said light detectors 202, 203 and are adapted to amplify the output signals from these light detectors; numeral 206 a differential amplifier adapted to amplify the difference of the outputs between the preamplifier 204 and the preamplifier 205; numeral 207 a lock-in amplifier adapted to provide the DC approximated signal by receiving the AC output signals from the differential amplifier 206 and approximating them by excluding the differential component due to noise signal affected by the external light in accordance with the phase of the modulated signal received from the optical chopper portion 213 to be described; numeral 208 a comparator adapted to compare the output of the lock-in amplifier 207 with the reference value (OV for example in the present embodiment) and thus determine the irradiated position of the object 200 to be surgically operated; numeral 209 a laser control part adapted to control the output of the laser light for surgical operation by receiving the signal determining the irradiated position provided by said comparator 209; numeral 210 a power supply source for the laser light for surgical operation output of which is controlled by the laser control part 209; numeral 211 an oscillation tube part for the laser light for surgical operation adapted to generate the laser light for surgical operation by receiving the output of the laser supply power source 210; numeral 212 the laser supply source for the collimation light having a power source incorporated therein and adapted to generate the collimation laser light by the oscillation tube; and numeral 213 an optical chopper part adapted to optically modulate by means of a modulated signal the collimation laser light provided by the laser supply source 212 for the collimation light so as to separate the collimation light from the external light. It is to be noted that the laser light for collimation provided by the optical chopper part 213 and the laser light for surgical operation provided by the oscillation tube part for generating the laser for surgical operation are both conducted by the multi-articulation mirror of a known laser scalpel of multi-articulation mirror type and the optical axis of both laser lights are combined so that they are directed to the emission end 201 for the laser lights.
FIG. 3 is the vertical sectional view of the laser light emission end 201 shown in FIG. 2 wherein numeral 214 designates a hollow cylindrical body which is cylindrical in the configuration, the tip end portion thereof is inclined toward the central axis and also the tip end of which is provided with a circular opening; numeral 215 a multiplicity of inner layer optical fibers of which tip end portions are provided along the outer wall of said hollow cylindrical body 214 and which are disposed in a manner that a multiplicity of circular lateral sectional portions of said inner layer optical fibers surround the periphery of the annular sectional portion of said hollow cylindrical member 214; numeral 216 an orientation cylinder member having a constant wall thickness which is so provided as to surround the circumference of said inner layer optical fibers 215 at the inclined portion of said hollow cylindrical body 214, and has a similar configuration to said inclined portion of the hollow cylindrical body 214 as well as an opening still ahead of the opening of said hollow cylindrical body 214; numeral 217 a multiplicity of outer layer optical fibers the tip end portions of which are disposed along the outer wall of said orientation cylinder 216 concentrically with said inner layer optical fibers 215; and numeral 218 the laser light for collimation emitted in alignment with the central axis of said orientation cylinder 216. Further, it is to be noted that the input ends of the inner layer optical fiber 215 and the outer layer optical fiber 217 are located substantially on the surface of the opening of the hollow cylindrical body 214 and inclined relative to the laser light 218 for collimation. It is also to be noted that the light detectors 202 and 203 as shown in FIG. 2 are provided respectively at the output ends of the inner layer optical fibers 215 and outer layer optical fibers 217.
Operation of the illustrated apparatus will now be explained. The laser light for collimation generated by the laser supply source 212 for the collimation laser light is converted into the intermittent light by means of the optical chopper part 213 and directed to the emission end 201 for the laser light. The laser light 218 for collimation is emitted from the laser emission end 201 and caused to intermittently irradiate the object 200 to be surgically operated. The light reflected from the object 200 to be surgically operated by said intermittent irradiation and the external light (the reflect light comprising only that of the external light while the intermittent collimation laser light 218 is not emitted to the object 200 to be surgically operated) are provided to the inner layer optical fibers 215 and the outer layer optical fibers 217 depending on the position of the object 200 to be surgically operated. The reflect light conducted and provided respectively by said inner layer optical fibers 215 and the outer layer optical fibers 217 are respectively received by the light detectors 202 and 203. The output signals of which magnitude depends on the light value provided by the light detectors 202 and 203 are amplified respectively by the preamplifiers 204 and 205 so that the differential output of said output signals is picked up by the differential amplifier 206. The lock-in amplifier 207 is adapted to receive said AC differential output and provides the approximated DC output by excluding the differential component of the noise signal affected by the external light in accordance with the phase of the modulated signal received from the optical chopper part 213. The output of the lock-in amplifier 207 is converted to the positive signal when the irradiated position on the object 200 to be surgically operated is closer to the side of the orientation cylinder 216 than the position of the indefinite distance range (cf. .DELTA.l.sub.1 in FIG. 4) to be determined by the orientation cylinder 216 and described later in connection with FIG. 4 while it becomes a negative signal when said irradiated position is farther from the orientation cylinder 216 than position within said indefinite distance range. When said irradiated position is within said indefinite distance range, the output of the lock-in amplifier 207 becomes an indefinite signal either O, positive or negative depending on the reflective condition of the object 200 to be surgically operated as it will be explained later. The comparator 208 provides the output as the result of comparison between the output of the lock-in amplifier 207 and the reference value, for example OV. Depending on the result of said comparison, a signal of lower level is provided if the output of the lock-in amplifier 207 is a positive signal and a signal of higher level is provided if said output is a signal of less than OV. The laser control part 209 is adapted to control the laser power supply source 210 in such a manner that the oscillation tube part 211 for providing the laser for surgical operation may be caused to oscillate only when the signal of lower level is provided by the comparator 208. Thus, when the output of the comparator 208 is at a lower level, the oscillation tube part 211 for supplying the laser for surgical operation is caused to oscillate so as to supply the laser for surgical operation. The laser for surgical operation is conducted by the multi-articulation mirror and emitted out of the laser emission end 201 in combination with the laser light 218 for collimation whereby the former laser will irradiate the portion of the object 200 to be surgically operated where the laser 218 for collimation irradiates. Because of this irradiation, the object 200 to be surgically operated may be removed by burning it with the laser light for surgical operation.
Fig. 4 shows said indefinite distance range to be determined by said orientation cylinder 216. In Fig. 4, numeral 215 designates the inner layer optical fibers; numeral 215A the inner-most-edge of the input end of said inner layer optical fibers 215; numeral 216 the orientation cylinder; numeral 216A the outer-most-edge of the opening of said orientation cylinder 216; numeral 216B the inner-most-edge of the opening of the orientation cylinder 216; numeral 217 the outer layer optical fiber; numeral 217A the outer-most-edge of the input end of the outer layer optical fiber 217; and numeral 218 the laser light for collimation. The boundary line at which the inner layer optical fibers 215 may receive the reflected light of the laser light 218 for collimation is limited by the line L.sub.1 which is defined by connecting the extension of the edge 215A and the edge 216B. In other words, the reflected light derived from the position at upper side from said line L.sub.1, that is the position closer to the opening of the orientation cylinder 216 than the boundary line formed by the line L.sub.1, may be received by the inner layer optical fibers 215, while the reflected light derived from the position at lower side from said line L.sub.1 will be interrupted by the orientation cylinder 216, so that it will not be received by the inner layer optical fibers 215. Similarly, the boundary line at which the outer layer optical fibers 217 may receive the reflected light of the laser light 218 for collimation is limited by the line L.sub.2 which is defined by connecting the edge 217A and the edge 216A. The reflected light which comes from the upper side than said line L.sub.2 will be interrupted by the orientation cylinder 216 and not received by the outer layer optical fibers 217 while the reflected light coming from the position at lower side than said line L.sub.2 or farther from the opening of the orientation cylinder 216 with the line L.sub.2 as the boundary line may be received by the outer layer optical fibers 217. Accordingly, the reflected light derived from the region A indicated by hatching which is defined by the lines L.sub.1 and L.sub.2 may be received by both the inner layer optical fibers 215 and the outer layer optical fibers 217. Numerals 219 and 220 respectively represent the point where the laser light for collimation 218 crosses with the line L.sub.2 and the line L.sub.1. The distance range .DELTA.l.sub.1 defined by said crossing points 219 and 220 represents the indefinite distance range defined by the abovementioned orientation cylinder 216. As long as the object 200 to be surgically operated is located within said indefinite distance range .DELTA.l.sub.1, both the inner layer optical fibers 215 and the outer layer optical fibers 217 may receive the reflected light of the laser light 218 from the object 200 to be surgically operated. However, the light values received by said optical fibers are not necessarily the same depending on the surface condition of the object to be surgically operated. Especially when the surface of the object 200 to be surgically operated contain certain glitterness and the reflected light involves much of the light component reflected by the mirror, the nature of the output signal provided by the lock-in amplifier 207 as shown in FIG. 2 or the position determined by the comparator 208 may be subject to variation depending on which optical fibers, the inner layer optical fibers 215 or the outer layer optical fibers 217 will receive said reflected light. In other words, the indefinite distance range .DELTA.l.sub.1 serves as the erroneous range for the position determination. If the irradiated position of the object 200 to be surgically operated is located closer to the side of the opening of the orientation cylinder 216 than the crossing point 219, the reflected light of the laser light 218 for collimation is received only by the inner layer optical fibers 215 and the lase light for surgical operation is provided as earlier explained. On the contrary, if the irradiated position of the object 200 to be surgically operated is located at a position farther from the opening of the orientation cylinder 216 than the crossing point 220, the reflected light of the laser light 218 for collimation is received only by the outer layer optical fibers 217, the laser light for surgical operation will not be provided as earlier mentioned.
Now coming back to FIG. 1, it is assumed that the configuration of the tip end of the outer cylinder 109 is made the same as that of the tip end of the hollow cylindrical body 214 and the inner layer optical fibers 215, the orientation cylinder 216 and the outer layer optical fibers 217 are attached at the outer periphery of said tip end portion as shown in FIG. 3.
FIG. 5 shows the indefinite distance range when the orientation cylinder 216 and so forth are applied to be emission end for laser light of the laser scalpel shown in FIG. 1. Since numerals 215, 215A, 216, 216A, 216B, 217, 217A, 110 and 111, and the symbols L.sub.1, L.sub.2, A and .DELTA.l.sub.1 have been explained, the explanation thereof will not be repeated here. The laser light 110 or 111 for collimation is inclined similarly to the inclination of the orientation cylinder 216 and to the inclination of the boundary lines L.sub.1 and L.sub.2. Accordingly, the crossing points defined by the laser light 110 for collimation or the laser light 111 and the boundary lines L.sub.1 and L.sub.2 are respectively represented by 114 and 113. The indefinite distance range .DELTA.l.sub.2 defined between the crossing point 113 and the crossing point 114 becomes naturally larger than the range .DELTA.l.sub.1 and this means that the distance in which the indefinite position determination has to be done will be correspondingly much larger, causing the apparatus in question to be less practical. In other words, if an apparatus for preventing erroneous emission for the laser scalpel of a multi-articulation mirror manipulator type is applied directly to the apparatus for preventing erroneous emission for the laser scalpel of an optical fiber type, there has been such a problem wherein the indefinite distance range in which the position determination which justifies the emission of the laser light for surgical operation has to be indefinite will be wider thus making it impossible for the apparatus to be put into practical use.